This invention relates to a process for the manufacture of 1,4-bis(4-phenoxybenzoyl)benzene (sometimes referred to hereinafter as BPBB) in a hetereogeneous system, in the presence of a perfluorosulfonyl resin catalyst, which can be readily separated from the liquid phase in the reaction mixture.
BPBB, which is an important intermediate in the preparation of polyetherketone resins, can be made by condensation of 1,4-benzenedicarbonyl chloride with diphenyl ether in the presence of a Friedel-Crafts catalyst, usually aluminum chloride, which is employed in an amount of at least three moles per mole of 1,4-benzenedicarbonyl chloride. Diphenyl ether normally is used in a significant excess to minimize formation of higher oligomers. Normally, the reaction is carried out in a solvent such as, e.g., 1,2-dichlorobenzene, at a temperature of approximately -10.degree. C. After the reaction is complete, methanol is added to precipitate the product and remove aluminum chloride therefrom. The product is filtered off, washed repeatedly with methanol, and recrystallized from N,N-dimethylacetamide.
Use of aluminum chloride catalyst presents various shortcomings. Aluminum chloride, which is soluble in hot 1,2-dichlorobenzene, tends to contaminate the BPBB product, thus requiring repeated washings for its removal from the product and finally recrystallization of BPBB. The recovered aluminum chloride cannot be reused and this creates a waste disposal problem as well as adds to the cost of the operation. Finally, aluminum chloride does not have a high para-isomer selectivity, so that it tends to also produce a fair proportion of the ortho-isomer, i.e., 1,4-bis(2-phenoxybenzoyl)benzene or mixed isomer.
It would be desirable to be able to produce BPBB in a simpler operation, which would result in a good yield of a high purity material free of ortho-isomer and catalyst contamination, so that the additional purification steps could be avoided, and the overall reaction yield could be increased.